An electron linear accelerator may generate high energy electron beams or thus generate X-rays by having high energy electron beams hit a target. The radiotherapy is a processing technology that makes an irradiated article generate certain biological and physical effects by means of the ionization capability and the Bremsstrahlung effect of electron beams or X-rays, thereby treating tumors. Generally, in the radiotherapy, the focus area of a patient is firstly imaged and located with an analog localizer, and the radiation therapy is conducted with regard to the set therapy area based on the imaging-located results by an electron linear accelerator. According to the current demand, it is desired that the imaging and the radiotherapy could be achieved without moving the patient. For this demand, the prior arts mainly had the X-ray machine and the linear accelerator mounted at different angles of the Gantry or at different places of the treatment room respectively to perform the imaging and the radiotherapy without moving the patient. Some deviations would occur due to the different imaging angles and the different radiotherapy angles. Additionally, X-rays generated by low energy electron beams were used to conduct the imaging and high energy electron beams or the X-rays were used to conduct the radiotherapy by means of the energy switching technology of the electron linear accelerator. However, in this case, the quality of the imaging is poor because it is difficult for the low energy electron beams to be lower than 100 KeV.
The nondestructive inspection technique is to inspect the internal construction of an object by means of the penetration capacity of X-rays to the object. Recently, it is proposed to employ X-rays of two energy spectra, which are generated by electron beams having two levels of energy hit a target, to alternately conduct the radiation imaging with regard to the inspected object, and thereby identify the material features of object. This application needs a quick switching of the energy of the electron beams, and requires the energy difference between electron beams to be as large as possible. In the prior art, the quick adjustment of the energy of the electron beams generally was carried out by changing power and frequency of microwaves and the load of electron beams. In this case, the adjustment range of the electron beams is limited and the imaging quality deteriorates.